The present invention relates to a new and improved construction of an apparatus containing a work surface heated with a heat carrier medium. The present invention further pertains to a new and improved method and apparatus for the fabrication or manufacture of grooves or the like in a workpiece or body, such as the core cylinder of a heated cylinder, particularly, although not exclusively, the heated cylinder or press roll used in a papermaking machine.
In its more specific aspects, the present invention relates to an apparatus containing a work surface heated with a heat carrier medium, preferably steam. The work surface can be constituted, in particular, by a heated mold, a heated press punch, a heated press roll or a heated press plate or a heated cylinder, respectively, for instance for papermaking machines. The work surface is located upon a heat- or thermally-conducting surface layer, especially sheet metal plating or the like, for instance the cylinder jacket or shell. This heat-conducting surface layer is carried by a metallic base body or base member, for instance a core cylinder. The base body, for instance the core cylinder, is provided with grooves at its surface confronting the heat-conducting surface layer, especially the sheet metal plating or the like and/or this surface layer, especially the sheet metal plating, is provided with grooves at its surface confronting the base body, for instance the core cylinder. These grooves constitute a number of grooves which are preferably mutually parallel and, for instance, if desired, extend at least in part parallel to the axis of the core cylinder. Heating of the work surface, especially the mold or the cylinder is accomplished by infeed of the heat carrier medium, especially steam, into the grooves. As mentioned, the invention is particularly concerned with a cylinder or roll, especially for use in papermaking machines, for instance drying, crepe or calender cylinders or the like, and which cylinder or roll is heated by a heat carrier medium, especially steam.
Such type of cylinders or rolls, when used in process technology, serve to render possible a high heat or thermal energy transfer from the heat carrier medium, especially steam, to the cylinder surface. This is particularly of significance for drying cylinders and crepe cylinders in the papermaking industry.
There are known drying cylinders or crepe cylinders which, while functioning as pressure vessels, are charged with saturated steam up to a pressure of about 10 bar. Due to condensation, heat arrives at the medium or material which is to be heated up by means of the cylinder jacket or shell. Particular measures are undertaken in order to maintain the condensate film thickness as thin and uniform as possible. The measures which were used for this purpose entailed the employment of siphons and scoops, for instance. A prerequisite for the uniform thermal effects at the medium is that there is present as uniform as possible thermal pattern or course along the generatrix of the cylinder. It is for this reason that there are required exact internal machining and numerous siphons.
With such type of cylinders attempts have been made to maintain the heat transfer surfaces free of condensate film in order to economically improve the heat transfer. This has been done, for instance, due to the use of internal rib structure and so forth. Furthermore, to increase the heat transfer attempts have been made to achieve higher temperatures and higher steam pressures. However, the increasing wall thickness counteracts enhanced heat transfer. Yet, in order to overcome this problem, and at the same time to render possible pressure and temperature increases, there have been provided, for instance, bending-resistant, drying cylinders.